Self-venting caps for containers have been proposed utilizing flexible tubes with floats, but these are not wholly satisfactory because when the container is on its side, or tilted, the float tends to lie on its side also, so that fluid may splash into the tube and out the vent in the cap. The present invention provides a structure for venting vapor but not liquid from a liquid filled container particularly in cases where there can be vapor evolution which could cause the container to expand or burst, and clearly this is to avoided especially with corrosive liquids.
U.S. Pat. No. 3,672,533 describes a float which maintains itself in an upright position by being relatively large requiring an unconventional bottle with a wide neck and being of a special design to keep the float floating upright like a boat through proper weight distribution. This patent discloses a closure or cap with an orifice, so that it is self-venting, i.e. to the atmosphere.